Merge branch 'ab/grep-pcre2-allocfix'

Updates to memory allocation code around the use of pcre2 library.

* ab/grep-pcre2-allocfix:
  grep/pcre2: move definitions of pcre2_{malloc,free}
  grep/pcre2: move back to thread-only PCREv2 structures
  grep/pcre2: actually make pcre2 use custom allocator
  grep/pcre2: use pcre2_maketables_free() function
  grep/pcre2: use compile-time PCREv2 version test
  grep/pcre2: add GREP_PCRE2_DEBUG_MALLOC debug mode
  grep/pcre2: prepare to add debugging to pcre2_malloc()
  grep/pcre2: correct reference to grep_init() in comment
  grep/pcre2: drop needless assignment to NULL
  grep/pcre2: drop needless assignment + assert() on opt->pcre2

builtin/grep.c

@@ -1181,6 +1181,5 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		run_pager(&opt, prefix);
 	clear_pathspec(&pathspec);
 	free_grep_patterns(&opt);
-	grep_destroy();
 	return !hit;
 }